1. Field of the Invention
The present invention relates to an electromechanical transducer having a drug cup-shaped rotor or stator winding, and a method and apparatus for producing same.
2. Description of the Prior Art
Various kinds of cylindrical rotor/stator windings have been known.
For example, in the U.S. Pat. No. 3,191,081 to Faulhaber, issued on June 22, 1965, there is disclosed a method for manufacturing a cylindrical winding with a zigzag winding arrangement. In the U.S. Pat. No. 3,360,668 to Faulhaber, issued on Dec. 26, 1967, there is disclosed a method for manufacturing a cylindrical winding in accordance with a zigzag step winding by using pins so that a wire is swung in the axial direction of a winding core, thereby winding a wire stepwise. In the U.S. Pat. No. 3,441,761 to Painton et al, issued on Apr. 29, 1969, there is disclosed a method for manufacturing a cylindrical winding in which a wire is wound around a winding core in a hexagonal manner and is then crushed, thereby manufacturing a cylindrical winding. In addition, there has been known a method for manufacturing a cylindrical winding in which a single coil of hollow rectangular whirlpool like configuration is butt arranged to the surface of a cylinder so as to produce a cylindrical winding. In any of the above mentioned methods, attempts have been made to form a cylindrical winding which, in projection, has a rhombic shape or the like.
As is well known, an output shaft torque T may be provided by the following formula.
That is, EQU T=BgSZI/2.pi.a,
where
Bg is the magnetic flux density, PA1 S is the effective area, PA1 I is the electric current, PA1 Z is the total number of conductors, and PA1 a is the number of circuits arranged in parallel.
The torque T becomes maximum in case the projection contour of turns of the cylindrical winding is rectangular.
When the projection contour of the winding is rhombic, the torque T becomes one-half that of a cylindrical winding having a rectangular projection contour.
By the way, various kinds of motors such as a coreless motor, slotless motor, brushless motor and the like have recently been required to be made compact, particularly in thickness, while keeping a good performance and a rapid response without inertia. It has been desired to make the cylindrical winding have a long cylinder of a small diameter to ensure a good efficiency thereof for use in these various kinds of motors. It is also desired to provide a compact, over-square or flat rotor/stator winding with a high output power. In such a winding, a top or bottom portion is used as a magnetically effective or active region.
FIG. 36 is an illustration of a cylindrical winding of a rectangular cross section. Since a wire 502 extends along the peripheral surface of a cylindrical core 501 in parallel with its axis, the wire 502 is bent at a right angle at the end surfaces 503, 504 so as to pass through the center thereof and this operation is repeated around the periphery of the cylindrical core 501 so as to produce the cylindrical winding of the rectangular cross section, the wire is concentrated so as to overlap each on another at top and bottom center portion 505, 506 of the cylindrical core 501, thereby causing a drawback in that it is difficult that this cylindrical winding is put into practical use.
As the cylindrical winding of a rectangular cross section in projection, the wire is provided along the edges at the ends to form an opening thereat. In this case, however, the wire is concentrated so as to overlap each on another at the edges at the ends. Hence, it is difficult that the cylindrical winding is put into practical use.
FIG. 37 is a view of a winding according to the disclosure of the above described U.S. Pat. No. 3,191,081 and U.S. Pat. No. 3,360,668, showing that the wire 502 is wound around the peripheral surface of the cylindrical core 501 in such a manner as to present a rhombic configuration, thereby producing the cylindrical winding. In this case the wire 502 is wound in such a way as to present the rhombic configuration to produce the cylindrical winding, it becomes possible to prevent the wire 502 from being concentrated so as to overlap each on another. However, the torque to be generated becomes one half in comparison with the cylindrical coil winding of a rectangular projection. This is therefore unsatisfactory because of its poor performance.
FIG. 38 is a view of a winding according to the disclosure of U.S. Pat. No. 3,793,548 which shows an improvement of the cylindrical winding as shown in FIG. 37. Since the wire 502 is provided so as to be along with the edges 507, 508 at the ends, the wire 502 is concentrated to overlap each on another at the portions as indicated by reference numerals 509, 510. Therefore, it is difficult that this constitution is put into practical use.
More specifically, the above-described U.S. Pat. No. 3,793,548 shows a tangentially directed hexagonal pattern winding forming a hollow right-circular cylindrical rotor winding as shown in FIG. 38. As described above, U.S. Pat. No. 3,191,081 and U.S. Pat. No. 3,441,761 disclose a rhombic pattern and a hexagonal pattern, respectively. In the rhombic pattern, the effective area S is represented as follows: EQU S.congruent.DL/2&lt;DL
where D is the diameter and L is the height of the rotor winding. The relationship represents a reduction of effeciency in the rhombic pattern in comparison with the rectangular pattern shown in FIG. 36. In case of an axially elongated hexagonal rotor winding, the effective arear S is represented as follows: EQU S.congruent.DL.sub.1 -DL.sub.2 /2&lt;DL
where L.sub.1 is the length of a rectangular section of the hexagonal pattern and L.sub.2 /2 is the height of a triangular sections, L (longer length between the two opposite apexes) being represented by the sum of L.sub.1 +L.sub.2.
According to the disclosure of U.S. Pat. No. 3,793,548, tangentially directed inactive head portions causes an excessive wire overlapping or pile-up which results in difficulty in realizing such a winding. At the same time, as a matter of fact, such a pattern forms a three-dimensional hexagonal pillar or column and it is impossible to form a flat cylindrical winding.